It’s Okay to Store Data in Apache Kafka's distributed log

Is there anyone here running Kafka in production as primary data store for an web application backend? Did you write a very custom integration (or indeed a ES architecture), or did it just fit into existing (MVC) frameworks?

I appreciated the mid-article note that "treating Kafka as a primary store does mean raising the bar for how you run it". Databases and filesystems are silently scary.

Previous discussion here: https://news.ycombinator.com/item?id=15258547

I have nothing to do with Confluence or Kafka, but I really hoped there would be some more discussion then. Therefore the repost.